Excuse me for being ignorant on this, but I don't understand why every article I read about finding Alien life, the scientists claim to be looking for Earth like planets that could have life on them?

Is this the only way they think life could exist? With planets that are similar to earth?

No possibility of creatures swimming in lava or living without oxygen, breathing in something else. If we're talking extraterrestrial Aliens, try envisioning Aliens living in a environment that's nothing like ours.

It's true that life may take different forms than life as we know it. However the probability of life as we know it existing in the universe is 1. Life as we know it exists in the universe - on this planet! We don't know for sure if life could evolve on a planet made of molten aluminium. We do know for sure that life can exist on a planet covered in liquid water.

Earth like planets are the low handing fruit of exobiology. An earth like planet in an area which can sustain liquid water is the most likely place to find extra terrestrial life.

Oh and one other thing: Detecting life at great distances is hard. Detecting water at great distances is not.

It's true that life may take different forms than life as we know it. However the probability of life as we know it existing in the universe is 1. Life as we know it exists in the universe - on this planet! We don't know for sure if life could evolve on a planet made of molten aluminium. We do know for sure that life can exist on a planet covered in liquid water.

Earth like planets are the low handing fruit of exobiology. An earth like planet in an area which can sustain liquid water is the most likely place to find extra terrestrial life.

Oh and one other thing: Detecting life at great distances is hard. Detecting water at great distances is not.

It requires a great deal more than that for a planet to be inhabitable by humans. And planets are barely detectable by spectroscopy, they mostly detect them through their gravitational effects. In most cases no, one cannot know if liquid water is present. They mostly just say "well, this planet is near the habitable zone, so..."